Electrical terminal assembly



Nov. 29, 1960 E. s. SNADER ELECTRICAL TERMINAL ASSEMBLY 2 Sheets-Sheet 1 Filed Feb. 17, 1960 INVEN TOR. 5921.5 5. YA/405E Nov. 29, 1960 E. s. SNADER ELECTRICAL TERMINAL ASSEMBLY 2 Sheets-Sheet 2 Filed Feb. 17, 1960 INVENTOR. E'AELE S S V/905,2.

United States Patent 2,962,541 ELECTRICAL TERMINAL ASSEMBLY Earle S. Sunder, .Ellicott City, Md., assignor to Koppel-s Company, Inc.,'a corporation of Delaware Filed Feb. 17, 1960, Ser. No. 9,344 3 Claims. (Cl. 174-18) This invention relates generally *toelectrical terminals and more particularly to insulated terminal assemblies adaptable for use with fluid transformers and rectifiers or rectifiertransformer combinations.

conventionally, fluid .emersed transformer rectifiers and the like have been provided with electrical terminals mounted vertically on the top cover of the fluid containing rectifier transformer housing. It is often desirable, as in electrostatic precipitator installations, to mount terminals at other locations .such as on the sides of the housing to permit removal of the rectifier transformer housing top cover and provide access to the transformer windings and diode assembly for repairs and replacements without disturbing the terminals, bushings, or high voltage bus ducts running to the electrostatic precipitator. In addition, such side-mounted horizontal electrode terminals on a rectifier transformer are advantageous because they permit .the use of shorter, high voltage bus ducts which run at alower elevation with respect to the electrostatic precipitator electrode mountings so that readily available, inexpensive, standard insulated support housings may be employed.

Notwithstanding the advantages anddesirability of the side-mounted terminal structure, prior attempts to provide fluid-filled .rectifier transformers and the like with sidemounted horizontal electrical terminals and bushings have not been successfully employed because of various difiiculties. These difliculties have'been primarily caused by the .fact that side-mounted terminals are located below the fluid level on the typical rectifier transformer housing such that inthe event the insulating mounting structureof the terminal, -that is the bushing, is broken by impactjor flash over at the terminal, excessive fluid flows from the housing. The loss of fluid reduces the insulation about'the transformer rectifiersuch that the latter fails upon continued operation.

It is, accordingly, an object of the present invention to provide, an electricalterminalccnnection which is suitable for mounting on vthe side of afluid-filled rect'fier housing and which overcomes -the difficulties encountered heretofore.

It is a further object to provide a side-mounted electrical terminal and insulated bushing combination which is compact, readily removable and inexpensive to replace.

The terminal assembly of the present invention comprises generally an inner terminal mounted on a fluid-filled housing and electrically insulated therefrom; an outer terminal mounted on said housing in a spaced relation with respect to said inner terminal; and a telescopic terminal connector adapted to be placed between said inner terminal and said outer terminal. By such novel and advantageous assembly and arrangement, particularly with reference to fluid-filled rectifier transformer terminals and electrically insulated bushings therefor, the above mentioned advantages may be accomplished and the disadvantages of the prior art avoided.

The above and other objects and novel features of the invention will more fully appear from the terminal assembly as hereinafter described and claimed. It will be obvious to one skilled in the art to which the present invention pertains that various changes can be made in the arrangement, form, construction and type of various elements disclosed without departing from the scope .or spirit of the invention.

Referring now to .the accompanying drawings wherein like parts are numbered alike:

Fig. 1 isaside elevational view, partly in section, of one embodiment of the present invention shown in connection with a fragmentary view of a fluid-filled rectifier transformer housing.

:Fig. .2 is an enlarged side elevational view, partly in section, of the .telescopic terminal connector disclosed in Fig. 1.

Fig. 3 is an enlarged side elevational view, partly in section, of another embodiment of the electrically insulated sealing arrangement for the terminal assembly disclosedin Fig. 1.

Referring noWto the figures an inner electrical terminal 10is mounted within a substantially fiat electrical insulator 12 to form an assembled unit which is fixed within an opening provided therefor on the side of a fluid-containing housing 14. The electrical insulator 12 is preferably formedby pouring fluid resin or porcelain into a fiat mold supporting the inner terminal 1t) and a frame 16 having a substantially vU-shaped cross section about its periphery. When suitablyhardened, the resin or porcelain insulator 12, the fixed terminal 10 and the mounting frame 16 are removed fromthe mold as a single unit and mounted by welding in an openfng provided therefor in the side of rectifier transformer housing 14.

, Alternately, as shown in Fig. 3, terminal 16} may be mounted on the side of rectifier transformer housing 14 in a'manner which permits removal and disassembly of the electrode unit comprising terminal 10, insulator 12 and supporting frame 16. TermInal 10 is provided with a continuous groove 18 of rectangular cross-section about its circumference for retaining an elastomeric O-ring seal 20, the vouter diameter of which is slightly larger than the outer diameter of the inner terminal Jill. A porcelain disc-shaped insulator 12 is formed with an axial bore of Which the diameter is sufficiently large to permit insertion of terminal 10, but smaller than the outer diameter of C ring seal 20. In this manner, a fluid seal is effected between the insulator 12 and the inner terminal 10. To firmly hold the insulator 12 in place over the O-ring seal 20, terminal 10 is provided with threads whereby nut 22 and nut 24 may be tightened against opposite sides of said insulator 12. Surrounding the periphery of insulator 12 is a U-shaped, elastomeric seal 26 which prevents fluid leakage from the rectifier transformer housing 14 when thegassembly compr'singterminal it), insulator 12, O-ring seal20 and seal 26 is attached totheopening in thehousing 14 by means of frame 16 and nut and stud assemblies To prevent breakage of insulator 12 due to contamination, a tapered porcelain bushing 34 is adhered to a collar 32 by cement 31. The collar 32 is mounted by welding or by nut and stud assemblies 34 so as to surround the insulator receiving opening provided in the rectifier transformer housing 14. An electrically conductive cap 36 is cemented on the outermost convergent end of the bushing 30 to provide a completely sealed terminal housing and an outer electrical terminal 38 for receiving one end of a resiliently loaded removable terminal connector 40 the other end of which is forceably engaged with the fixed inner terminal 10 in a manner to be described be ow.

In accordance with the present invention, a telescopic terminal connector 40 is employed to provide an electrical connection between fixed terminal 10 and bushing terminal 38. The terminal connector 40 comprises two preferably cylindrical members 42 and 44. The member of larger circumference 42 is formed with an axially oriented central bore 46 of which the diameter is slightly larger than the diameter of the smaller member 44 so that said larger member 42 telescopes with slight clearance over said smaller diameter member 44. A resilient member 48, preferably in the form of a helical compression spring as shown in Fig. 2, is placed at the base of the central bore 46 of member 42 to exert an axial force between said member 42 and member 44 when the latter has been inserted within the former and the complete terminal connector 40 wedged between the fixed electrodes 1t) and 38. To insure alignment of terminal connector 40 and positive contact thereof between immovable terminals and 38, the distal ends of members 42 and 44 are formed in the shape of cones 50 and 52 respectively, the apexes of which are forced into engagement by resilient member 48 with the respective apexes of conically concave ends 54 and 56 provided therefor in terminals 38 and 10.

To prepare the terminal assembly of the present invention for operation, high voltage output lead 58 from the transformer (not shown) is attached to the internal threaded extremity of inner terminal 10 by clamping cable connector 60 between nut 62 and nut 64 respectively. The sealed fixed assembly made up of frame 16, insulator 12 and terminal 10, is inserted in an opening provided therefor in housing 14 and mounted therein by welding or by nut and stud assemblies 28 about its periphery. Collar 32 is then secured by welding or by nut and stud assemblies 34 concentrically about insulator 12 on the outside of housing 14. On the top portion of collar 32, a tap bolt 66 is provided for introducing an insulating fluid medium into bushing chamber 68. Another tap bolt 70 is located on the bottom portion of collar 32 to provide an outlet for draining the insulating fluid medium from chamber 68 when bushing 30 is to be replaced or otherwise removed.

Tapered bushing 30 is secured to the side of rectifier transformer housing 14 by cementing the divergent end thereof into collar 32. The telescopic terminal connector 40 is then introduduced from the convergent open end of bushing 30 into bushing chamber 68 and one end of said connector 40 is held in engagement with fixed terminal 10. Bushing terminal 38 located on the inner surface of bushing cap 36 is engaged with the other end of telescopic terminal connector 40 and then cemented onto the convergent end of bushing 30. It can readily be seen that bushing terminal 38, when secured, compresses terminal connector 40 against the forces exerted by the spring 48 so as to hold the connector 40 firmly between the terminals 38 and 10, thereby effecting a positive electrical connection therebetween.

An electrical conductor in the form of a bus bar 72 leading to a device to be energized such as, for example, an electrostatic precipitator (not shown) is connected to the threaded outer end of bushing terminal 38 by nut 74 or other suitable means. A bus bar housing 76 is attached to studs 78 located on rectifier transformer housing 14 to provide an electrically grounded shield over the entire terminal assembly and bus bar conductor 72.

Prior to operation, rectifier transformer housing 14 and terminal bushing 30 are filled with an insulating fluid medium by introducing said fluid into chamber 80 through an opening (not shown) provided in rectifier transformer cover 82 and into chamber 68 through the upper tapped opening 66 provided in collar 32. The fluid medum may be any type of electrical insulating oil having high dielectric strength and which is capable of withstanding high voltages as, for example, transformer mineral oil. The insulating oil serves to prevent destructive corona discharge and sparkover between conducting components which carry high voltages and components which are grounded, and further serves to prevent contamination of insulator 12.

Thus, by the present invention, it can readily be seen that in the event of breakage of the side mounted electrode bushing 30, protective insulating fluid is prevented from leaking out of rectifier transformer housing 14, thereby preventing destruction of transformer components. The only insulating fluid lost is that within bushing chamber 68 which is readily and inexpensively remedied by replacement in accordance with the present invention.

What is claimed is:

1. A terminal assembly for power equipment having a housing and fluid within said housing, said assembly comprising a plate-like insulating member mounted in a wall of said housing, an inner terminal mounted in said insulating member and having one end exposed to the exterior of said housing and the other end to the interior thereof, a hollow insulating bushing having one end fixed to said housing about said insulating member and the other end spaced from said housing, an outer terminal mounted in said other end of said bushing and a telescopic electrical connector means connecting said inner and outer terminals.

2. The invention as defined in claim 1 in which said assembly is provided with means for mounting said insulator member in fluid tight relation in the wall of said housing.

3. The invention as defined in claim 1 in which said telescopic means includes two members and resilient means between said two members for urging the opposed ends thereof into engagement with said inner and outer members.

References Cited in the file of this patent UNITED STATES PATENTS 1,672,357 Watson June 5, 1928 1,873,977 Naef Aug. 30, 1932 2,396,871 Meyerhans Mar. 19, 1946 

